April 12

Culturing Organisms

Batch Culture

  • Organism in housed in a enclosed vessel
    • Cannot grow exponentially
  • Nutrient concentration affects both growth rate and growth yield
    • Low concentrations- Growth rate is submaximal since nutrients cannot be transport into the cell fast enough to satisfy metabolic demand
    • High concentrations- maximal growth rate may be obtained, but the cell density can continue to increase in proportion to the concentration of nutrients in the medium
  • Growth Curve describes the growth cycle
    • Lag Phase
    • Exponential phase
    • Stationary Phase
    • Death Phase
  • Lag Phase
    • Brief or extended time frame
    • Inoculum taken from old culture
      • Lag is present due to cells being deprived of key nutrients
    • Lag present if inoculum is low of viability(few live cells)
    • Lag is present if cells are damaged but not killed by stressor(Temperature, radiation, toxic chemicals)
    • Lag is observed when microbial culture is transferred from a rich to poor culture
  • Exponential Phase
    • Cell population doubles at regular intervals for a brief or extended period
      • Depends on available resources and other factors
    • Cells are in their healthiest state
    • Rate of exponential growth is influenced by environmental conditions( temperature, composition of culture medium) and genetic characteristics
    • Prokaryotes grow faster than eukaryotes
    • Small eukaryotes grow faster than larger ones
  • Stationary Phase
    • No net increase or decrease in cell number and thus the growth rate of the population is zero.
    • Energy metabolism and biosynthetic processes may continue at reduced rate
  • Death Phase
    • Rate of cell death is slower than rate of exponential growth and viable cells remain in culture for months or years
    • Cryptic Growth- Exponential and Death phases balance each other out


Posted April 12, 2017 by andrew in category Learning Summary

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